We shrank a 1440×900 PNG screenshot to 1280 pixels wide with our own Resize tool, and the file grew from 119 KB to 187 KB. Nothing broke. PNG stores flat colour cheaply and blended colour expensively, and scaling a screenshot down turns every sharp edge into a run of in-between shades.
That one result explains most PNG frustration. PNG is lossless, so when you compress a PNG without losing quality, a tool can only look for a tighter way to write down the same pixels. On a file that was saved sensibly in the first place, that search is worth a quarter of the size or less. Our view after the tests below: for screenshots, stop squeezing the PNG and change the format.
Four PNGs, five ways to save them
We took four PNGs: a 1440×900 screenshot of a pricing page (flat colours, buttons, some text), a 1200×1600 screenshot of a page that is almost all text, a 960×300 logo on a transparent background, and a 1408×768 photo that had been saved as PNG. Each went through the encoders our free tools use, at the settings they use. The repacked column is what the Compress tool does to a PNG when you pick “Every pixel exact”: OxiPNG rewrites it losslessly. Lossless WebP is what you get from PNG to WebP with the quality slider at 100.
| File | Original | PNG repacked (lossless) | WebP lossless | WebP 85 | JPG 90 | JPG 95 |
|---|---|---|---|---|---|---|
| Pricing-page screenshot, 1440×900 | 119 KB | 74% | 43% | 45% | 97% | 128% |
| Text-heavy screenshot, 1200×1600 | 264 KB | 69% | 29% | 49% | 96% | 129% |
| Logo on a transparent background, 960×300 | 28 KB | 72% | 64% | 32% | 73% (background turned white) | 93% |
| Photo saved as PNG, 1408×768 | 1.47 MB | 96% | 72% | 6% | 14% | 21% |
Start with the repacked column, because it is the honest answer to anyone shopping for a PNG compressor. OxiPNG took 26 to 31% off the three graphics and 4% off the photo, with every pixel identical to the original. It is slow, too. On a fast laptop it took 1 to 1.5 seconds per screenshot and 1.5 seconds for the photo. The photo barely moved because fine photographic detail looks like noise to PNG’s compression, and noise can’t be written down more tightly.
Lossless WebP makes the same promise, every pixel back, in a newer format. It beat the repacked PNG on all four files: by 42% on the pricing page, 58% on the text page, 25% on the photo and 10% on the logo. We ran that column outside the tool page with the same WebP encoder and settings, then decoded each file and compared it with the source. Every visible pixel matched. On the logo, colour values hidden under fully transparent pixels changed, which nobody can see.
Google’s WebP page says lossless WebP images are 26% smaller than PNGs. The study behind it measured 23% against PNGs optimised with ZopfliPNG, on 12,000 translucent PNGs taken from the web. Our photo landed close to that figure. Our screenshots did about twice as well, and our only transparent file, the logo, did less than half as well. Four files can’t overturn a 12,000-image study. They do show that what the picture contains moves the saving more than the choice of lossless format does, so one headline percentage for “PNG” tells you little about your file.
The lossy columns are where the size goes. WebP at 85 cut the two screenshots by 51 to 55% and still measured closer to the original than JPG. On SSIM, a standard similarity score where 1 means identical, WebP 85 scored 0.999 on the pricing page against 0.995 for JPG 85, and 0.9985 against 0.9905 on the text page. It also beat JPG 95 on both, at about a third of JPG 95’s size.
JPG is the trap: at quality 95 it made both screenshots 28 to 29% bigger than the PNGs they started as.
Our PNG to JPG converter starts at 90. That saved 3% on the pricing page and 4% on the text page. Not worth it. JPG was designed for photographs, and a screenshot is close to its worst case: few smooth gradients, which JPG stores cheaply, and hard edges everywhere, which it stores badly. On the photo saved as PNG the same converter was the right call, 86% smaller at 90.
Fewer colours is the lossy trick
Some PNG compressors return a PNG that is far smaller than anything in our repacked column. TinyPNG explains how on its own site: similar colours are combined, a technique it calls quantization, and 24-bit PNGs “can be converted into much smaller 8-bit indexed color images.” An 8-bit indexed PNG holds at most 256 colours. A logo drawn in three flat colours loses nothing you’d notice. A photo, or a screenshot with antialiased text and soft shadows, has its extra colours replaced by near neighbours, and smooth gradients can break into bands.
The result is still a PNG file, but the compression was lossy. Since 24 September 2026 our Compress tool does this too, and it is the default there: under “PNG files” it offers “Smaller file”, which keeps the fewest colours (up to 256) that still look like the original, chosen for each image, next to “Every pixel exact”. On five other test PNGs (three photos, a logo on a transparent background and a 2880×1800 screenshot of our home page), Smaller file at the default quality of 75 kept 128 colours in each photo and cut them by 75 to 80%, the logo by 81% and the screenshot by 71%. You can drag across each result to compare it with the original, and change the quality for one image alone. The converters that save to PNG still keep every pixel unless you switch. If a tool promises lossless PNG compression and hands back a file 70% smaller, count its colours before you believe it.
Resizing a screenshot can make it bigger
Back to the opening number. Fitting the pricing-page screenshot within 1280 pixels gave a 1280×800 PNG at 157% of the original size. The text page, scaled to 960×1280, came out at 136%. The pixel counts fell by 21% and 36%, and the bytes went up anyway, because the smooth resampling that suits photos replaces each crisp edge of each letter with graded shades PNG compresses poorly.
We found this in our own Resize tool, and it now flags the case: when a resized PNG comes out bigger than the file you gave it, a note under that file says so and suggests WebP. It still hands you the bigger PNG. Compress can fall back to your original picture when its output grows, but a resize asked for new dimensions, so the original is no answer there. Pick WebP under “Save as” in the same tool when you resize screenshots.
What we would do with each kind
- Screenshots and pages of text: save as WebP with PNG to WebP, at 85, or at 100 if every pixel has to survive. Both came out at least 29% smaller than the repacked PNG.
- Logos with a transparent background: WebP 85 kept the transparency and cut ours to 32%. Keep a PNG copy for design apps that won’t open WebP.
- Photos saved as PNG shouldn’t be PNGs. JPG 90 took 86% off ours; WebP 85 took 94%.
- A file that must stay PNG because a form or a print shop insists: run it through Compress. Smaller file cut our test PNGs by 71 to 80%; pick Every pixel exact if nothing may change, and take the 4 to 31%.